/Engine/Source/Runtime/Experimental/GeometryCollectionEngine/Public/GeometryCollection/GeometryCollectionISMPoolComponent.h
Structure containing a set of allocated instance ranges in anFGeometryCollectionISMwhich is the manager for a single ISM component. The instance ranges don't change once allocated, and aren't the same as the actual render indices in the ISM. The reason that we don't store the the actual ISM render indices is that ISM component is free to reorder its instances whenever it likes.
struct FInstanceGroups
TArray<FInstan...
FreeList
TArray<FInstan...
GroupRanges
int32
TotalFreeInstanceCount
int32
TotalInstanceCount